Conventional compression-ignition (CI) engines in use today for vehicular and other industrial uses are fueled by a high grade fuel oil known as "No. 1 or No. 2 grade" and as "diesel fuel." It is a petroleum based fuel, high in hydrocarbons, has good lubricity characteristics which assists in lubricating the injectors and other moving parts exposed to the fuel prior to its being introduced into the combustion chamber, and is ignitable with or without the assist of a glow plug at relatively low geometric compression ratios ranging up to as much as 19:1.
However, with the advent of concern over reducing nitrogen oxides, particulates, highly reactive hydrocarbons and other combustion by-product emissions into the environment, there has been increased design effort in maximizing the emission characteristics of this fuel. Some have been cost effective (i.e. higher performance and greater thermal efficiencies), while others have not (i.e. the addition of particulate traps).
Coincident with these emission concerns, has been the concern of petroleum-based fuel shortages and the need for alternative fuel sources. Among the alternatives considered are low cetane liquid fuels, such as methanol and ethanol, as well as low cetane gases, such as natural gas.
Methanol is a particularly attractive fuel alternative since it is a liquid fuel, therefore, compatible with known liquid fuel systems. Additionally, methanol is a by-product of natural gas, an abundant energy resource. The special properties of methanol, however, require major engineering changes in engine design and the design of the air supply and fuel systems, just to name a few.
U.S. Pat. No. 4,539,948, issued to Toepel and assigned to the assignee of the present invention, describes an internal combustion engine of the two-cycle compression-ignition type for handling methanol fuels whereby the scavenging, i.e. clearing the exhaust gases from the combustion chamber immediately following combustion, is controlled so as to allow a certain amount of hot residual gases to remain in the combustion chamber to support and promote the auto-ignition of the methanol fuel during the next power cycle.
U.S. Pat. No. 4,502,283, issued to Wandel and assigned to the assignee of the present invention, discloses an automatically actuated valving arrangement for routing the engine blower discharge air through a bypass of the combustion chamber-cylinder liner air box upon the sensing of a particular air pressure. Thus, the full air delivery capacity of the blower is either fully utilized in assisting the combustion process, or completely removed therefrom.
U.S. Pat. No. 4,738,110, issued to Tateno, discloses a diesel engine equipped with a mechanically driven charger. The engine comprises an exhaust-gas driven turbocharger, a mechanically driven charger positioned in the engine intake passage, connection control means for controlling the mechanical connection between the mechanically driven charger and the engine, a bypass passage connected to the intake passage downstream of the charger and valve means controlling a bypass air flow within the bypass passage. The engine further includes control means for controlling the connection control means and the valve means in response to output signals from a plurality of detecting means for detecting starting and operation of the engine.
U.S. Pat. No. 4,394,812, issued to Mezger, discloses a supercharged internal combustion engine for motor vehicles. The engine has an exhaust gas turbine driven supercharging blower, exhaust gas bypass for regulating the exhaust gas turbine by diverting exhaust gases around the turbine and a blow-off valve control charging air bypass for circulating charging air supplied from the blower. The engine also has a second charging air bypass for circulating a portion of the air supplied by the blower therearound in response to at least one engine operating parameter so as to provide protection against excess charging pressure. The at least one engine parameter includes engine speed and/or charge pressure. A solenoid valve controlled by a safety switch may be utilized to control opening of the second bypass.
Despite these prior efforts, until the present invention, there was no two-cycle CI engine in use, fueled solely by methanol or any other low cetane liquid fuel. Despite the knowledge represented by the above-mentioned prior art, and other expertise in the field, there were many problems to be overcome for the successful long-range CI engine having satisfactory durability and performance. The present invention is directed to those major remaining concerns.